Cambrian Explosion

When terrestrial strata and the fossil record are examined, it is to be seen that all living organisms appeared simultaneously. The oldest stratum of the earth in which fossils of living creatures have been found is that of the Cambrian, which has an estimated age of 500-550 million years.

The living creatures found in the strata belonging to the Cambrian period emerged all of a sudden in the fossil record. There are no pre-existing ancestors.

A half-billion years ago, the remarkably complex forms of animals we see today suddenly appeared. This moment, right at the start of Earth's Cambrian period, some 550 million years ago, marks the evolutionary explosion that filled the seas with the world's first complex creatures. The large animal phyla of today were present already in the early Cambrian and they were as distinct from each other as they are today.
-- "Mysteries of the Orient", Discover, April 1993, p.40.

How the earth came to overflow with such a great number of animal species all of a sudden and how these distinct types of species with no common ancestors could have emerged is a question that remains unanswered by evolutionists...

And to the one under me, fair play to you for your wu, but the suffix with all that insinuated personal reference - kicking in the balls etc. It's just plain rude, unecessary and a little below the belt (ahem!)

PS: rp - If you wish to apologise then take out the abusive crap, oh and by the way, I don't have balls... I have ovaries.

PPS: rp - Thank you for editting out the initial abusive language, and thus apology accepted.

The main event in the Cambrian explosion is the development of the ability to use chalk, crystallized CaCO2, to form supporting structures within the body.

From a purely construction technical point of view, this is a major breakthrough. With a skeleton, the body can grow larger, more solid, and lighter. New kinds of structures, with great advantages, suddenly become technically feasible: jaws, teeth, spines, claws, shields, limbs, wings, lungs.

So it really isn't surprising to find an enormous diversification of life forms, an 'active exploration' of the new area of possibilities opened up by hard bone construction. Once the ability is there, it is easy, biotechnologically speaking, for bone structures to grow to different sizes, which allows a different overall body size and different shapes of body parts.

It's even less surprising to see these life forms suddenly appear in the fossil record: the hard, chalk-based parts of the body are the only parts that fossilize well. When remains of a creature are found, it is very rare to find traces of anything but the chalk part; for creatures that don't possess a chalk skeleton, it is very rare to find any remains at all.

So while the Cambrian explosion may be an explosion of life, at its core it's an explosion of chalk. (As a matter of fact, all chalk in nature consists of the remains of chalk-producing organisms.)

A case in point; the eye. The eye doesn't fossilize: it doesn't contain any hard parts. What we really find in these post-explosion fossils is not eyes, but eye sockets! Eye sockets of hard bone are new and clearly beneficial: eyes are important and worth being protected. But the sudden appearance of eye sockets doesn't mean that the eye itself didn't exist long before.

It should be mentioned that the development of multicellular life forms with chalk skeletons didn't happen overnight, and many intermediate forms can be found on earth today. We can think of a multicellular organism as a huge colony of single cells that stick together and coerce each other into specializing into specific functions. (Some of the mechanisms and principles of this coercion are already known to science.) This specialization could come into being within creatures that already form colonies, but with little or no specialization among the cells. Examples of such creatures living today are sponges and corals.

It's easy to see how the use of chalk within the body may have developed gradually. Cartilage is structurally similar to bone tissue, but instead of hard crystallized chalk, it contains collagens; it is viscous enough to provide some rigidity, but still flexible, and too soft to fossilize. Cartilage is an important building material in life forms. There is nothing to contradict the evidence that creatures with hard bone have developed from predecessors with skeletons of weaker tissue, creatures that already contain most of the same organs, but are too soft to fossilize.

Jellyfish, for instance, owe their body shape and size to this type of tissue - note that some jellyfish, like the Portuguese man-of-war, are actually colonies of jellyfish-like organisms, rather than single multicellular beings.

Another example: we, the vertebrates, have developed from primitive fish with skeletons entirely made out of cartilage; sharks are among this type of fish.

(A personal note. My primary response to rk2001's writeup is not nearly as reasonable as what you see above. I feel outrage and shame upon seeing such views exposed in public. What would you do if you met someone who claimed, right into your face, that airplanes don't exist? They are heavier than air, so they cannot possibly fly! It's all a matter of clever illusion! Let's see how the avionicists answer that! What do you do, get angry? Roll your eyes, write the person off as a loss to reason, and change the subject? Or do you patiently point out that evidence to the contrary is all around, that the actual principles that allow airplanes to fly are well known and start to explain them? I really don't know the answers to that question.
Hurray to the civilizing powers of E2.)

PS to rk2001; if you feel it is inappropriate or rude to describe how your writeup makes me feel, my apologies.
PPS to LoMeta: Thank you. Good to know that the scientific jury is still undecided on what explains this event. In any case, the above shouldn't be treated as gospel.

About one-tenth of the first write-up* above is fact; the rest is rubbish. Before 1950 or thereabouts it could have had some place in a scientific discussion. The persistence of this ignorance today is very disturbing.

There was abundant complex life before the Cambrian explosion, of many different kinds, including animals. There is no good evidence that the present phyla that became widespread in the Explosion actually originated in it.

The basic fact is this: the Cambrian transition shows when hard body parts evolved. Ancient history is told in terms of pots because baked clay survives better than baskets. That doesn't make pots more important or more numerous than baskets. Palaeontology is constricted into a jigsaw-puzzle of bones, teeth, and shells because those are the bits that are left lying around abundantly and indestructibly. It has got very little to do with what evolved when, or how, or how long it took, or why.

Molecular evidence from the DNA of animals suggests they may have existed, as sexual animals, from 1.2 Gyr ago. There is some evidence that eukaryotic algae from the Bitter Springs deposit in central Australia may have been sexually reproducing 900 million years (900 Myr) ago. A more conservative DNA analysis, disallowing some genes, puts the origin of animal life at 700 Myr ago.

Around then, 700 or 670 Myr, was the first great explosion in complex, diverse, multicellular life. The Ediacaran or Vendian fauna has been found all over the world. There was a multiplicity of soft-bodied creatures resembling jellyfish, worms, sponges, and many others. The impressions of their bodies can be beautifully preserved. In many cases these don't look ancestral to modern phyla, however: they appear to be an independent world-wide blossoming of complex life, as the oxygen-rich atmosphere kicked in. It lasted for 100 to 150 million years, only overtaken by the next two diversifications, the Tommotian (in the early Cambrian) and the main Cambrian explosion.

The Cambrian Explosion proper (c. 570-540 Myr) is famous for its radiation of every Bauplan (blueprint, or body-layout) of the modern animal world: arthropods, chordates, annelids, molluscs, and so on. No wholly new animal phylum is known to have evolved since then. It was a tremendously important event in the evolution of life. But four-fifths of the history of life had already happened.

Another explosion has taken place in the last forty years: our understanding of the richness and variation that had already happened before it. No serious scientist believes the Cambrian forms came out of nowhere at the beginning of the Cambrian. What we are seeing is a change in body form that allowed bodies, previous invisible, to become visible.

It affected not only animals, but many other kinds of creatures known from solid fossil evidence to have existed for many hundreds of millons of years beforehand, if not thousands of millions: foraminifera, algae, radiolarians, and so on. This suggests a global change (in the oceans, the only inhabited environment at that time), a shift in the balance of nutrients perhaps. The continuing discovery of our evolution is one of the most beauiful adventures our human intellect is privileged to share.

Any good biologist worth his or her salt (or should I say calcium carbonate?).....and yes I am a biologist, will tell you that this controversial theory, and that is exactly what it is, speculative conjecturing, is far from settled.

Strata of Cambrian rock were first studied in Wales by British biologist Adam Sedgewick(1785-1873), who named the period for ancient Wales (Lat.Cambria). Geologists in many areas of the world employ a variety of classification systems some characterized by the presence or absence of trilobites. Cambrian rocks are found in Europe, North America, Newfoundland, eastern Canada, various countries of South America and Asia. As far as my personal research can determine all Cambrian fossils found thus far were saltwater dwellers; the plant dwellers of the period are seaweeds, and the animal fossils are invertebrates. The Cambrian Period is also known as Biology’s Big Bang and the Cambrian Explosion because of its great diversity of life.

Even Charles Darwin, a Christian scientist, was skeptical about the Cambrian Explosionhypothesis. The idea was attractive to the Church as The Deity of Evolution. A great way to explain the sudden appearance of life without the evidence of interim fossils...that evolution was a sudden burst of activity with ensuing periods of little change. So we now had a reasonable speculation for the sudden appearance of life (supported by numerous fossils) in the Cambrian Period, implying that the Cambrian was a pulse of rapid evolution. Darwin believed more along the lines that evolution progressed at a more even pace and it was only a matter of finding fossils under the Cambrian strata.

'I cannot doubt that all the Siluriantrilobites have descended from some one crustacean, which must have lived long before the Silurian age....Consequently, if my theory be true, it is indisputable that before the lowest Silurian strata was deposited, long periods elapsed, as long as, or probably longer than, the whole interval from the Silurian to the present day.....The case must at present remain inexplicable; and may be truly urged as a valid argument against the views here entertained'...... it is indisputable that before the lowest Silurian stratum was deposited, long periods elapsed, as long as, or probably far longer than, the whole interval from the Silurian age to the present day; and that during these vast, yet quite unknown periods of time, the world swarmed with living creatures. To the question why we do not find records of these vast primordial periods, I can give no satisfactory answer. 1

Time ran out and Darwin was unable to find this strata leaving the Church only able to assert that that life appeared at one moment: in the Cambrian Explosion created by God. Today along with science and technology, scientists are still speculating about the evidence of Darwin’s hypotheses. Fossils under the Cambrian strata, known as the Vendian or Ediacaran suggest that multicellular life existed even before the Cambrian Period and surely lends a lot of credibility to Darwin's ideas.

It bears repeating because rk2001 states it very clearly in her summarizing statement: "How the earth came to overflow with such a great number of animal species all of a sudden and how these distinct types of species with no common ancestors could have emerged is a question that remains unanswered by evolutionists..."

Encyclopedia references go on to say in part:

.....reasons for (the Cambrian Explosion) are still debated, but a leading theory is that the amount of oxygen in the atmosphere had finally reached levels that allowed large, complex animals to exist. Oxygen levels may also have facilitated the metabolic processes that produce collagen, a protein building block that is the basis for hard structures in the body.

A recent issue of Scientific American, Life Goes for a Spin
A topsy-turfy earth may have triggered an evolutionary big bang, tells an even more far reaching speculation that is garnering attention:

Scientists have advanced many theories to explain that big bang in the diversification of life, none of them fully convincing. Now Joseph L. Kirschvink of the California Institute of Technology and his colleagues believe they may have solved what he calls "one of the outstanding mysteries of the biosphere." Life on the earth turned upside down, Kirschvink proposes, because the earth itself turned upside down: an abnormally rapid reorganization of the earth's crust, tens of times faster than normal continental drift, touched off sharp climatic shifts that in turn unleashed a torrent of evolutionary change.

The repeated reorganizations in global wander during a true polar wander event should have fragmented any large-scale ecosystems that were established, generating smaller, more isolated populations and leading to a higher evolutionary branching rate among existing groups." the researchers say with confidence in their postulation in the July 25, 1997, issue of Science.

Their hope is that their theory of polar wander will become an additional instrument in the understanding the geology and biology of the Cambrian Explosion. This analysis is however by no means meant to be considered as conclusive proof of the explanation of the Cambrian Explosion. All good scientists keep open minds and form objective opinions based on the current evidence. Like the other possible explanations presented here, such as physiological theories of fossilization and geneticstudies gathered here can be added to the many other theories abounding such as the appearance of the first true carnivores and the role they may also have played.

Given all together these explanations are still only tools in man's feeble attempt to explain the nature of this indeed as rk2001, states so accurately a miraculous event, the explanation of which still remains beyond the visible and observable universe.